Even with all of the known health risks, recent evidence suggests that up to 15% of women smoke during pregnancy and only 18-25% of women who smoke will stop when they find out they are pregnant. Prenatal consumption of nicotine has been correlated with a number of severe health issues, as well as behavioral and cognitive impairments in childhood. Therefore, it is of great importance to identify and treat children at risk from the early months of life before patterns become stable and more difficult to change. Adverse outcomes could be mitigated by appropriate interventions, but first the specific mechanisms that link prenatal exposure to poor social-emotional and cognitive outcomes and trajectories must be more closely examined. The proposed pilot study aims to elucidate such mechanisms. Pathways between prenatal exposure to cigarettes and infant social-emotional and cognitive outcomes at 9 months will be explored, with a focus on the mediating role of infant sleep. In addition, this study aims to examine whether paths differ for infants as a function of caregiving, and will attempt to differentiate between the effects of general caregiving behavior (i.e., sensitivity) and behavior at bedtime/through the night, which might influence outcomes via its effect on infant sleep quality. The current study will recruit 120 women during their second trimester of pregnancy (80 smokers, 40 non-smokers). Maternal cigarette and other substance use will be assessed during pregnancy, and a piece of the umbilical cord will be collected and analyzed (at birth) to evaluate prenatal exposure to nicotine. Moreover, infant saliva will be analyzed for current exposure to environmental tobacco smoke at each age. At 3 months, video cameras will be set-up in multiple locations to capture parent-infant interactions at bedtime and through the night to evaluate specific caregiver practices and emotional availability, and infants will wear an Actiwatch, to record movement during sleep, for seven days, and at 9 months infant biobehavioral functioning (behavioral, parasympathetic, sympathetic response at rest and during challenge) and cognitive functioning will be assessed. Finally, At 3 and 9 months of age caregiver-infant interactions will be video recorded in the home for later coding of parenting behavior. Mentored training in conducting the proposed prospective and longitudinal pilot study within this high-risk population, as well as utilizing cutting edge methods for assessing fetal and infant cigarette exposure and observational measures of sleep, will establish a strong foundation for submitting an R01 grant proposal in the latter years of this award. The knowledge gained over this period will also lay the groundwork for my long-term goal of developing interventions for families at risk.